The following is a list of references, which is intended for a better understanding of the background of the present invention.
Carter, A. D. Herbicide movement in soil: principles, pathways and processes. Weed Res. 2000, 40, 113–122.
Dailey, O. D.; Dowler, C. C.; Mullinix, B. G. Polymeric microcapsules of the herbicides atrazine and metribuzin; preparation and evaluation of controlled-release properties. J. Agric. Food Chem. 1993, 41, 1517–1522.
El Nahhal, Y.; Nir, S.; Polubesova, T.; Margulies, L.; Rubin, B. Leaching, phytotoxicity, and weed control of new formulations of alachlor. J. Agric. Food Chem. 1998, 46, 3305–3313.
El Nahhal, Y; Nir, S.; Polubesova, T.; Margulies, L.; Rubin, B. Movement of metolachlor in soil: Effect of new organo-clay formulations. Pestic. Sci. 1999, 55, 857–864.
El Nahhal, Y.; Nir, S.; Serban, C.; Rabinovitch O.; Rubin, B. Montmorillonite-Phenyltrimethylammonium Yields Environmentally Improved Formulations of Hydrophobic Herbicides. J Agric. Food Chem. 2000, 48, 4791–4801.
El Nahhal, Y.; Nir, S.; Serban, C.; Rabinovitch O.; Rubin, B. Organo-clay formulations of acetochlor for reduced movement in soil. J Agric. Food Chem. 2001, 49, 5364–5371.
Ferraz, A.; Souza, J. A.; Silva, F. T.; Goncalves, A. R.; Bruns, R. E.; Cotrim, A. R.; Wilkins, R. M. Controlled release of 2,4-D from granule martix formulations based on six lignins. J. Agri. Food Chem. 1997, 45, 1001–1005.
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Use of agrochernicals, despite health and environmental problems associated with their use, is essential for producing the required amount of food, worldwide. One of the problems associated with their use stems from their mode of application. In order to achieve a pronounced effect, high doses of agrochemical are used in order to compensate for the fact that part of the agrochemical is “lost” to the environment. One mechanism of “losing” agrochemicals, and in particular, herbicides, is by leaching and surface migration. These mechanisms lead to a reduction in the efficacy of the applied herbicide leading ultimately to higher doses of herbicide that are costly both economically and environmentally. One of the environmental problems is associated with surface and groundwater contamination (Carter, 2000).
Slow and controlled release formulations aimed at prolonging the effect of the herbicide and inhibiting its migration to deeper layers of the soil were developed. These include, encapsulation using alginate (Gerstl et al. 1998), cyclodextrin complexes (Loukas et al. 1994), formulations with lignin (Ferraz et al. 1997), formulations with starch (Gish et al. 1994), formulations with organo-clay (El-Nahhal et al. 2000, 2001) and polymer capsulation (Dailey et al. 1993). It should however be noted that such formulations are specifically designed for hydrophobic herbicides. Anionic herbicides such as the sulfonylureas, imidazolinones and triazolopyrimidines can not be formulated as described above. Such anionic herbicides are weak acids and are negatively charged at moderate basic pH. In calcareous soils having a basic pH, these negatively charged herbicides leach to deep soil layers and migrate to non-target layers (Veeh et al. 1994; Pool et al. 1995; and Sarmah et al. 1998). Thus, despite the fact that these herbicides are very useful, their interaction with the environment renders their use inefficient, and higher doses than actually would be needed are applied in order to achieve the desired effect. Consequently, there is a need to provide efficient formulations of herbicides that are weak acid herbicides and are negatively charged at the pH of the soil they are applied into.